A robust high speed indoor wireless communications system using chirp spread spectrum

This paper considers the implications of using chirp spread spectrum (CSS) as an antimultipath modulation technique for the transmission of high speed (>10 Mb/s) data in the indoor wireless channel. Three elements are required for a CSS system to perform optimally in the multipath environment-a chirp spreader/correlator for resolution of the channel multipath, a phase-differential modulation scheme to co-phase the multipath components and a RAKE for recombination of the symbol energy. The advantage of CSS is that all three of these elements can be implemented with simple analog hardware. A prototype CSS system is presented along with simulated and measured performance plots in the indoor channel. Test results indicate that a CSS system using DQPSK can perform within 2 dB of Gaussian DQPSK in 10 m non-line of sight (NLOS) indoor channels with excess delay >200 ns, down to bit error rates of 10/sup -7/ with single omni antennas in transmitter and receiver and no coding, at data rates of 20 Mb/s and higher.